From DE 1 029 613 A, different piston crown shapes for self-igniting engines are known, which are to make possible a low-noise combustion through optimal feed and intermixing of the injected fuel. In this respect a description is given of providing the piston trough wall with axially parallel or spiral-shaped separation edges so that the fuel is guided into the favorable swirl flow prevailing in the middle.
In spark-ignition gas engines, pistons with different piston trough shapes are employed. As a rule, the following usual variants are distinguished:                A) Piston with roof-shaped piston crown. The piston crown is configured for combustion processes with gas-scavenged pre-chamber so that the flare jets strike the combustion chamber walls as late as possible.        B) Piston with tub-shaped piston crown. The piston crown is configured so that a tumble flow generated on the inlet side is retained.        C) Piston with omega piston trough. The piston crown is configured for optimal direct injection for diesel operation and is also employed with the gas spark-ignition engine for cost reasons and for the sake of simplicity; the latter, however, despite a possibly poor combustion profile.        D) Piston with pot piston trough. The piston crown is configured so that between piston margin and cylinder head a squish flow in radial direction is created. Furthermore, the swirl flow in the pot piston trough is intensified.        
For engines with swirl inlet ports and chamber plugs, pistons with pot piston troughs are highly suitable. During the compression stroke, the mixture above the piston crown margin (squish margin) of the piston is displaced into the pot piston trough. During the expansion stroke, the mixture is again sucked out of the pot piston trough. This process, in particular in the vicinity of the top dead centre, may lead to intense squish flows.
Complementarily to the squish flow, the pot piston trough also may lead to an acceleration of the swirl flow generated on the inlet side. Because of the rotary impulse retention, the rotational velocity of the swirl flow increases when the mixture is displaced to the inside into the pot piston trough.
The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of the prior systems.